This invention relates to display devices and particularly to thin film, electroluminescent (TFEL) display devices.
Light emitting display devices have been fabricated utilizing the electroluminescent effect obtained by exposing special light-emitting materials (sometimes called phosphors) to an electrical field. In order to provide high contrast in TFEL displays, it is known to provide a light absorbing (black) dielectric layer between the active layer of electroluminescent material and the back electrode as described in U.S. Pat. No. 3,560,784 to G. N. Steele, et al. It is also known to provide such a black background behind a transparent backside electrode and to make electrical connection to the transparent backside electrode through openings or border areas in the black background (U.S. Pat. No. 4,488,084 to S. G. Linfors, et al).
In addition to having high contrast, it is important for a TFEL display to have a long life. Unfortunately the high electric fields required to provide electroluminescense can cause sporadic breakdowns of the EL film in some locations, and these breakdowns can in turn produce a break in the continuity of the overlying electrode at such locations. To reduce these breakdowns, it is known to provide strips of insulating material under one side of each of the parallel strips of metal, thus reducing the electrical field in a "bus rail" portion of the backside electrodes (U.S. Pat. No. 4,342,945 to the present inventor, Richard D. Ketchpel).
These prior art techniques have helped increase the contrast and the life of TFEL displays. However, there is a continuing need to provide TFEL display structures which can be economically fabricated to provide high contrast, long life, and reliable quality.